Ukraine’s Third Army Corps says it used heavy bomber drones to deploy ground robots behind Russian lines during a secretive operation near Lyman.

The unit said Operation Vivaldi has helped bring 125 square kilometers under Ukrainian control, including 50 square kilometers that had been occupied by Russia.

The operation reportedly involved heavy drones carrying suicide ground robots more than 10 kilometers behind enemy lines, where uncrewed systems were used ahead of advancing infantry.

Ukraine’s Third Army Corps said its robots have completed more than 15,700 missions and delivered about 3,300 tons of cargo, while artillery and other uncrewed systems targeted Russian command posts, communications, logistics and reserves, Business Insider has reported.

The unit also said air defenses and electronic warfare helped protect the operation and counter Russian infiltration teams attempting to exploit gaps in Ukrainian defenses.